LIGAMENTS OF THE WRIST AND METACARPUS. 



321 



general capsular ligament enclosing synovial cavities separated by an interarticular 

 fibro-osseous septum composed of the bones of the first row and their interosseous 

 ligaments. Preparatory to the common description which follows, it is necessary to 

 consider the ligaments and relations of the groups of bones which take part in the 

 formation of the subdivisions of the general articulation. 



The pisiform being practically a sesamoid bone, the upper end of the carpus is 

 an egg-shaped articular surface made chiefly by the convexities of the scaphoid and 

 semilunar and to a small extent by the cuneiform (Fig. 340). These three bones 

 are united into one apparatus by two strong interosseous ligaments situated just 

 below the proximal ends of the bones, covered by synovial membrane and com- 



FiG. 340. 



Ulna f 



Triangular cartilage 

 Semilunar 



Interosseous - 

 carpo-metacarpal ^^,y, 

 ligament ///6'/, 



Dorsal ligament of first row 



Cuneiform 

 Os magnum 



Unciform 



Trapezium 

 Trapezoid 



Dorsal ligament of 

 second row 



Dorsal intermetacarpal ligaments 



Dorsal aspect of right wrist. The joint of ulna is opened and the shaft displaced forward and inward to show 

 under side of head. The radio-carpal, intracarpal, and carpometacarpal joints are shown by removing' the dorsal 

 ligaments and flexing the hand. 



pleting the articular surface. They completely shut of? the radio-carpal from the in- 

 tracarpal joint. The latter is concavo-convex, the co7icave part being formed by the 

 cuneiform, the semilunar, and the hollow surface of the scaphoid ; the convexity by 

 the lower surface of the latter bone, which articulates with the trapezium and trape- 

 zoid. The concavity amounts to a socket, of which the side formed by the scaphoid 

 is nearly at right angles to the base, while the inner, formed by the cuneiform, is 

 oblique. The scaphoid is attached to the semilunar much less tightly than is the 

 cuneiform, so that considerable motion occurs between them. The scaphoid, besides 

 sliding in various directions on the semilunar, can turn on an approximately trans- 

 verse axis through its proximal part, which permits of flexion and extension, to 

 some degree independent of the rest of the first row. Its lower end may also move 



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